Rotation transmissions of the built-in one-way clutch type have been used for example as a follower pulley that is fastened to the end of the rotating shaft of the alternator that is an automobile generator, or as the pinion etc. that is fastened to an end of the rotating shaft of the starter motor in the starting apparatus of an automobile, or have been used for transmitting rotation to auxiliary devices from a separate drive apparatus (motor) during idling stop while the engine is stopped.
An alternator is used for generating the necessary electrical power for an automobile, the drive source of which is the engine of the automobile. The construction of this kind of alternator has been disclosed for example in Japanese Patent Publication No. Toku Kai Hei 7-139550. FIG. 13 shows the alternator 1 that is described in this publication. The rotating shaft 3 is supported inside the housing 2 by a pair of rolling bearings 4 such that it rotates freely. In the middle section of this rotating shaft 3 there is a rotor 5 and a commutator 6. Also, a follower pulley 7 is fastened on one end of this rotating shaft 3 (right end in FIG. 13) in the section that protrudes out from the housing 2. When installed in an engine, an endless belt runs around this follower pulley 7 such that the engine can rotate and drive the rotating shaft 3 through the crankshaft.
Conventionally, a typical follower pulley 7 that was simply fastened to the rotating shaft 3 was used. However, in recent years, a rotation transmission apparatus with built-in one-way clutch has been proposed and has been used somewhat. For example, in a pulley apparatus with built-in one-way clutch, when the running speed of the endless belt is constant or when it is accelerating, power is transmitted from the endless belt to the rotating shaft, and when the running speed of the endless belt is decelerating, there is relative rotation between the follower pulley and the rotating shaft. A pulley apparatus with built-in one-way clutch having this kind of function has been disclosed for example in Japanese Patent Publications Nos. Toku Kai Sho 56-101353, Toku Kai Hei 7-317807, Toku Kai Hei 8-61443, Toku Kai Hei 8-226462, Toku Ko Hei 7-72585, and French Patent Publication No. FR2726059A1.
FIGS. 14 to 16 show one example of a prior art pulley apparatus with built-in one-way clutch as described in these publications. This pulley apparatus with built-in one-way clutch has an inner-diameter-side member, specifically a sleeve 8, that is fitted over the rotating shaft 3 of the alternator 1 (see FIG. 13). Also, there is a cylindrical outer-diameter-side member, specifically follower pulley 7a, that is located around this sleeve 8 such that it is concentric with the sleeve 8. In addition, there is a pair of support bearings 9 and a roller clutch 10, which is the one-way clutch, located between the outer peripheral surface of the sleeve 8 and the inner peripheral surface of the follower pulley 7a. 
The sleeve 8 has a generally cylindrical shape, and is fitted onto one end of the rotating shaft 3 of the alternator 1 such that it rotates freely with the rotating shaft 3. Therefore, in the example shown in the figure, there is a male screw section formed around the outer peripheral surface on the tip end of the rotating shaft 3, and a screw hole 11 is formed in the middle section around the inner peripheral surface of the sleeve 8, such that the screw hole 11 can be screwed together with the male screw section. Moreover, an attachment hole section 12, having a hexagonal cross section, is formed on the tip end (left end in FIG. 14) on the inner peripheral surface of the sleeve 8 such that the tip end of a tool such as a hexagonal wrench can be attached to this attachment hole section 12. Furthermore, the base end on the inner peripheral surface of the sleeve 8 (right end in FIG. 14) is a circular hole section 13 that can be fitted over the tip end of the rotating shaft 3 at a portion closer to the middle of it such that there is no play between them.
Construction of assembling the sleeve 8 and the rotating shaft 3 such that they do not rotate relative to each other can be accomplished as well using other construction such as a spline joint, non-circular fit, key joint, or the like. Also, the center section of the outer peripheral surface of the sleeve 8 is a large-diameter section 14 that has a diameter that is larger than the other sections.
On the other hand, the tip end half on the outer peripheral surface of the follower pulley 7a is formed with a wave shaped cross section along the width direction such that part of an endless belt, called a poly V-belt, can be placed around it. Also, the aforementioned roller clutch 10 is placed in the middle in the axial direction in the space between the outer peripheral surface of the sleeve 8 and the inner peripheral surface of the follower pulley 7a, and support bearings 9 are placed on both ends in the axial direction of this space such that they are located on both sides in the axial direction of the roller clutch 10, respectively.
Of these, the support bearings 9 support the radial load that is applied to the follower pulley 7a, and make it possible for the follower pulley 7a to rotate relative to the sleeve 8. In the example shown in the figures, ball bearings of the deep-groove type are used as the support bearings 9. In other words, each of these support bearings 9 comprises an outer race 16 that has an outer-ring raceway 15 of the deep-groove type formed around its inner peripheral surface, an inner race 18 that has an inner-ring raceway 17 of the deep-groove type formed around its outer peripheral surface, and a plurality of balls 19 that are located between the outer-ring raceway 15 and inner-ring raceway 17 such that they rotate freely.
Also, the outer race 16 is fitted into and fixed around the inner peripheral surface near both ends of the follower pulley 7a, and the inner race 18 is fitted onto and fixed around the outer peripheral surface near both ends of the sleeve 8. In addition, in this state, one surface in the axial direction of the inner races 18 comes in contact with one of the axially opposite end surfaces (stepped surface) of the large-diameter section 14, respectively.
Moreover, in the example shown in the figures, by placing seal rings 20 between the inner peripheral surface on the opposite ends of the inner races 16 and the outer peripheral surface on the opposite ends of the inner races 18, respectively, the openings on both ends of the spaces where the balls 19 are located are covered.
Also, of the openings on both ends of the spaces where the balls 19 are located, it is possible to place the seal rings 20 only at the openings on the sides of the outside spaces of the pulley apparatus. However, as in the example shown in the figure, in the case where the seal rings 20 are placed also at the openings on the sides of the inside spaces of the pulley apparatus, it is preferred that through-holes be formed through part of the seal rings 20 on the sides of these inside spaces in order that the space between the pair of support bearings 9 is communicated with the spaces where the balls 19 are located. The reason for this is that it prevents the pressure in the space between both support bearings 9 from rising excessively when pressing the support bearings 9 between the inner peripheral surface of the follower pulley 7a and the outer peripheral surface of the sleeve 8.
Also, the aforementioned roller clutch 10 transmits rotation force between the follower pulley 7a and the sleeve 8 only when the pulley 7a rotates in relation to the sleeve 8 in a specified direction. In order to form this kind of roller clutch 10, an inner ring 21 for the clutch is securely fastened around the large-diameter section 14 of the sleeve 8 through interference fit.
In this specification, the outer peripheral surface of the sleeve 8 will be called “one peripheral surface”, and the inner ring 21 for the clutch will be called the “protruding section”.
This inner ring 21 for the clutch is made from steel plate, such as carburized steel plate, and is formed into a generally cylindrical shape by using a plastic working process such as pressing, and a cam surface 22 is formed on its outer peripheral surface. In other words, a plurality of concave sections 23, called the ramp section, are formed at equally space intervals around the circumference on the outer peripheral surface of the inner ring 21 for the clutch, to form a cam surface 22 on the outer peripheral surface. This cam surface 22 can also be formed directly on the outer peripheral surface of the large-diameter section 14. In this specification, this large-diameter section 14 will be called the “protruding section”.
Of the inner peripheral surface of the outer ring 25 for the clutch, which is securely fitted into and fastened through interference fit in the middle section of the inner peripheral surface of the follower pulley 7a, at least the middle section in the axial direction that comes in contact with the rollers 26 (described later) is a simple cylindrical section. This kind of outer ring 25 for the clutch is also made from steel plate, such as carburized steel plate, and is formed into a generally cylindrical shape by using a plastic working process such as pressing, and inward facing flange-shaped collar sections 27a, 27b are formed on the axially opposite ends, respectively.
With respect to these collar sections 27a, 27b, the collar section 27a (left collar section in FIG. 14) is formed in advance when manufacturing the outer ring 25 for the clutch, so its material thickness is the same as the thickness of the cylindrical section of the outer ring 25 for the clutch. On the other hand, the other collar section 27b (right collar section in FIG. 14) is formed on the inside in the radial direction of the outer ring 25 for the clutch after the rollers 26 and the clutch retainer 28 (described later) are assembled, and therefore made thin.
Also, the plurality of rollers 26, which together with the inner ring 21 and outer ring 25 for the clutch make up the roller clutch 10, are supported in the clutch retainer 28, which is fitted around the inner ring 21 for the clutch and can not rotate with respect to the inner ring 21 for the clutch, such that they can freely rotate and displace a little in the circumferential direction. This clutch retainer 28 is made of a synthetic resin (for example, a synthetic resin such as polyamide 66, polyamide 46, or polyphenylene sulfide in which glass fibers are mixed by an amount of about 20%) formed into a generally basket-shaped cylindrical shape and comprises a pair of ring-shaped rims 29, and a plurality of columns 30 that link the rims 29 with each other.
Also, pockets 31 are defined by the inside surfaces of the rim sections 29 and the side surfaces in the circumferential direction of the columns 30. The pockets 31 hold the rollers 26 such that they can freely roll and slightly displace in the circumferential direction.
Moreover, the circular arc-shaped convex sections 32 are formed at a plurality of locations on the inner peripheral surface of each of the rim sections 29 and engaged with the concave sections 23 that are formed on the outer peripheral surface of the inner ring 21 for the clutch, so that the clutch retainer 28 is mounted on the inner ring 21 for the clutch such that it cannot rotate relative to the inner ring 21 for the clutch.
Also, there are springs (not shown in the figure), such as plate springs or synthetic resin springs, which are integrated with the clutch retainer 28 and located between the column sections 30 of the clutch retainer 28 and the rollers 26. There is a cylindrical-shaped space between the cam surface 22 and the inner peripheral surface (cylindrical surface) in the middle section of the outer ring 25 for the clutch. The aforementioned springs elastically press the rollers 26 in the circumferential direction of the clutch retainer 28 toward the section of the cylindrical-shaped space where the dimension of the width in the radial direction is narrower.
Moreover, the both axial end surfaces of the clutch retainer 28 closely face the inside surfaces of the collars 27a, 27b of the outer ring 25 for the clutch to prevent the clutch retainer 28 from displacement in the axial direction.
When using the pulley apparatus with built-in one-way clutch that is constructed as described above, the rollers 26 bite into the section where the width in the radial direction of the cylindrical-shaped space is narrower when the follower pulley 7a rotates in a specified direction relative to the sleeve 8, which makes it impossible for the follower pulley 7a to rotate relative to the sleeve 8. This state is called the locked state.
On the other hand, when the follower pulley 7a rotates in the opposite direction of the specified direction relative to the sleeve 8, the rollers 26 move out of the way to the section where the width in the radial direction of the cylindrical space is wider, and makes it possible for the follower pulley 7a to rotate freely relative to the sleeve 8. This state is called the overrun state.
There are the following two reasons for using a pulley apparatus with built-in one-way clutch for an alternator that has the construction described above.
The first reason is for extending the life of the endless belt. For example, when the drive engine is a diesel engine, and it is rotating at a low rpm such as during idling, fluctuation in the rotational angular velocity of the crankshaft becomes large. As a result, the running speed of the endless belt that extends around the drive pulley also fluctuates small. On the other hand, the rotating shaft 3 of the alternator that is rotated and driven by this endless belt by way of the follower pulley does not fluctuate so suddenly due to the inertia mass of the rotating shaft 3 and the rotor that is fixed to the rotating shaft 3.
However, when the follower pulley is just fastened to the rotating shaft, there is a tendency for the endless belt and follower pulley to rub in both directions due to the fluctuations in the rotational angular velocity of the crankshaft. As a result, stress acts repeatedly in different directions on the endless belt in a rubbing relation with the follower pulley, and accordingly it becomes easy for slipping to occur between the endless belt and the follower pulley, or the life of the endless belt becomes short.
Therefore, by using a pulley apparatus with built-in one-way clutch for an alternator as this follower clutch, rotational power is freely transmitted from the follower pulley to the rotating shaft 3 when the running speed of the endless belt is constant or increases, and conversely, the follower pulley rotates freely with respect to the rotating shaft 3 when the running speed of the endless belt decreases. In other words, when the running speed of the endless belt decreases, the rotational angular velocity of the follower pulley becomes slower than the rotational angular velocity of the rotating shaft, and thus prevents strong rubbing at the area of contact between the endless belt and the follower pulley. In this way, the direction of the stress acting on the area of rubbing between the follower pulley and endless belt is made constant, and thus prevents slipping from occurring between the endless belt and the follower pulley, and prevents a drop in life of the endless belt.
The second reason is for improving the efficiency of power generation of the alternator. The rotating shaft 3, to which the alternator rotor is fastened, is driven and rotated by the automobile drive engine by way of the endless belt and follower pulley. In the case of using a fixed follower pulley, when the rotational velocity of the drive engine drops suddenly, there is a sudden drop in the rotational velocity of the rotor, and the amount of power generated by the alternator also decreases suddenly.
By using a pulley apparatus with built-in one-way clutch for an alternator as the follower clutch of the alternator, the rotational velocity of the rotor drops gradually due to the inertial force and power generation continues even when the rotational velocity of the drive engine drops suddenly. As a result, in comparison to the case of using a fixed follower pulley, it is possible to increase the amount of power generated by the alternator by efficiently using the kinetic energy of the rotating shaft and rotor.
In the case of the prior art construction described above, displacement of the clutch retainer 28 in the axial direction is prevented by the pair of collar sections 27a, 27b that are formed on both ends of the outer ring 25 for the clutch. In other words, when the clutch retainer 28 tries to move in the axial direction during overrun when there is relative rotation between the follower pulley 7a and the sleeve 8, the inside surface of one of the collar sections 27a, 27b comes in contact (sliding contact) with the corresponding end surface in the axial direction of the clutch retainer 28, and prevents the displacement of clutch retainer 28 in the axial direction.
However, in the case of the pulley apparatus with built-in one-way clutch for an alternator described above, the relative rotational velocity between the pulley 7a and the sleeve 8 can reach from several hundred revolutions per min (rpm) to several thousand revolutions per minute in extreme cases. Therefore, when there is sliding contact between the axially opposite end surfaces of the clutch retainer 28 and the inside surfaces of the collar sections 27a, 27b, respectively, there is a possibility of wear of the axially opposite end surfaces of the clutch retainer 28, or there is a possibility that the friction heat that occurs due to sliding contact between the axially opposite end surfaces of the clutch retainer 28 and the inside surfaces of the collar sections 27a, 27b may become excessive.
Also, in the case that the powder generated due to wear of the axially opposite end surfaces of the clutch retainer 28 is mixed with the grease used for lubricating the roller clutch 10, there is a possibility that there will be a drop in the lubricating ability of this grease. Moreover, in the case that the friction heat, which is generated in the area of sliding contact, becomes excessive, there is a possibility that the grease will degrade quickly due to heat. Degradation of the grease causes the roller clutch 10 to lose durability and is not desirable.
These kinds of problems also occur in the case of construction where there is not a pair of collar sections 27a, 27b, and where the axially opposite end surfaces of the clutch retainer 28 come in sliding contact with another member that rotates relative to the clutch retainer 28.
Moreover, in the case of the clutch retainer that is disclosed in Japanese patent publication No. Toku Kai 2001-32911, which was assigned to the same assignee as the present invention, there are attachment sections on both sides in the axial direction of the clutch retainer, and when the clutch retainer is elastically deformed and fitted onto the inner ring for the roller clutch, the aforementioned attachment sections hold the inner ring for the roller clutch between them and limit displacement in the axial direction of the clutch retainer.
However, depending on the material of the retainer and the interference between the attachment sections and the inner ring for the roller clutch, there existed problems in that when elastically deforming the clutch retainer and fitting it onto the inner ring for the roller clutch, the retainer could break, or the interference would be too large, so that the fitting force would be too large making fitting difficult, or the interference would be too small, so that the clutch retainer would become separated easily.